1. Field of the Invention
The present invention relates to a sheet material feed apparatus for taking one by one from a plurality of stacked sheet materials and feeding the sheet material, and more particularly, it relates to a sheet material feed apparatus having a mechanism for preventing the simultaneous feed of a plurality of sheet materials, i.e., a so-called overlap feed (or multifeeding), and a printer, a copying machine, a printing apparatus, a facsimile, and a scanner having the sheet material feed apparatus.
2. Related Background Art
Conventionally, as a sheet material feed apparatus having an overlap feed preventing mechanism, there have been used as representative types, a retard roller method which forcibly rotates a separation roller in a reverse direction with respect to a sheet material feed direction via a torque limiter, a return lever method for operating a return lever for each predetermined number of sheet materials, so as to return the sheet material leading edge to a predetermined position, and the like.
Among the return lever methods, for example, there is a two-direction rotation control type disclosed in the U.S. Pat. No. 5,997,198 wherein a drive source of a feed apparatus is rotated in a forward direction for feeding a sheet material and the drive source is rotated in a reverse direction to operate the return lever so as to return the sheet material to a predetermined position. Moreover, as is disclosed in Japanese Patent Application Laid-Open No. 4-72242, there is a type using a clutch mechanism wherein the drive source of the feed apparatus is rotated in only one direction and a clutch mechanism is provided in a drive transmission mechanism, so that during a lever operation, the clutch mechanism operates the return lever.
However, in the aforementioned conventional technique, there are some restrictions for operating the overlap feed preventing mechanism.
In a sheet material feed apparatus of the retard roller method, it is necessary to use a torque limiter for maintaining an appropriate release torque and always rotate in the reverse direction during a feed operation. This complicates the mechanism, increases the apparatus size, and the production cost. Moreover, there has been a case to apply an unnecessary resistance force to the sheet material being fed.
Moreover, in the case of the two-direction rotation control type return lever method, both the rotation directions of the drive source such as a motor are used for automatic feed operation. Accordingly, it becomes difficult to use the drive source as a common drive source of the other mechanism. For example, in an entire recording apparatus including the sheet material feed apparatus, the number of drive sources is increased, which increases the apparatus size and production cost. Moreover, there is a case that the return lever is brought into contact with a sheet material to apply an unnecessary resistance force to the sheet material. Furthermore, since the return lever operation is performed after completion of a series of feed operation, it is necessary to provide a return lever operation time in addition to the feed operation, which tends to increase the apparatus operation time.
Moreover, in the sheet material feed apparatus of the type using the clutch mechanism, it is necessary to provide a clutch mechanism for controlling drive transmission, which requires a separate drive source such as a solenoid, or it is necessary to control the clutch mechanism by rotating the rotation drive source such as a motor in two directions. This complicates the mechanism, increases the apparatus size and the production cost. Moreover, similarly as the two-direction rotation type, it is necessary to provide a lever operation time in addition to the feed operation, which tends to increase the feed operation time.
Moreover, when setting sheet materials, in order to prevent protrusion of the sheet materials into a separation mechanism portion, the sheet material feed route is closed by closing a shutter in the retard roller method or by rotating the drive source in the reverse direction to stop the return lever at a predetermined position in the case of two-direction rotation type. Such a configuration complicates a control operation and mechanism, and increases the apparatus size and production cost. Moreover, similarly as the two-direction rotation type, it is necessary to provide a lever operation time in addition to the feed operation, which tends to increase the operation time.